The invention relates to a bristle for a broom, but more particularly, the invention relates to a bristle for use in a railway roadbed broom for moving ballast.
In forming a railway road bed, a ballast of crushed rock, such as lime stone, is layered underneath and distributed around railroad ties. The ballast elevation is preferably level with or just below the railroad ties. Initial installation and normal maintenance of the roadbed requires dumping new ballast over the ties and rails supported by and above the ties. As known in the art, the ballast is redistributed from its dumped location to its desired elevation by means of a rotary broom that has a plurality of individually replaceable bristles.
Early bristles were made from nothing more than discarded lengths of wire reinforced rubber hose where a twined wire reinforcement is layered between a rubber tube and cover. An example of such a broom is disclosed in U.S. Pat. No. 3,237,232.
The harsh operating bristle environment has lead to several bristle constructions having a goal of improving the life of a bristle made from hose. U.S. Pat. No. 3,649,984 discloses a bristle having a core made of a bundle of parallel spring-steel wires that are encased in a resilient sheath. U.S. Pat. No. 4,184,223 discloses a bristle made of a solid elastomeric stem with a forward projecting knob attached at one end as a forward wearing and driving surface. U.S. Pat. No. 4,367,564 discloses a bristle with two distinct elastomeric members with a reinforcement sandwiched therebetween; the first member has a "D" shape when viewed in cross section and the second member has a "U" shape when viewed in cross section.
Not only must such bristles flex or bend rearwardly when they impact and redistribute the movable ballast above a desired roadbed elevation, the bristles are required to bend even more as they impact the immovable rails located above the ties or as they impact the immovable ties.
An object of the invention is to provide a bristle with appropriate abrasion resistant characteristics and a configuration that enhances bending for improved life.